[PATCH 0/3] percpu-rwsem: introduce percpu_rw_semaphore->recursive mode

From	Oleg Nesterov <oleg@redhat.com>
Newsgroups	linux.kernel
Subject	[PATCH 0/3] percpu-rwsem: introduce percpu_rw_semaphore->recursive mode
Date	2015-06-29 02:00 +0200
Message-ID	<pGuEp-2Kv-1@gated-at.bofh.it> (permalink)
References	(2 earlier) <pEiR3-XU-1@gated-at.bofh.it> <pEqEW-409-31@gated-at.bofh.it> <pEzRU-vQ-15@gated-at.bofh.it> <pEAEj-1rm-19@gated-at.bofh.it> <pETnA-3eq-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 06/24, Oleg Nesterov wrote:
>
> So we need percpu_down_write_dont_block_readers(). I already thought
> about this before, I'll try to make the patch tomorrow on top of your
> changes.

Never say tomorrow...

> This means that we do not need task_struct->cpuhp_ref, but we can't
> avoid livelock we currently have: cpu_hotplug_begin() can never succeed
> if the new readers come fast enough.

Like with any other "recursive" lock.

Peter, I know you don't like the 1st patch. And yes, we could add another
mutex into percpu_rw_semaphore instead. But I think it would be better
to rely on rcu_sync_enter(). As for completion, we can remove it later.
Nevermind, the actual change is 3/3 and it looks simple.

Oleg.

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Thread

Re: [RFC][PATCH 09/13] hotplug: Replace hotplug lock with  percpu-rwsem Oleg Nesterov <oleg@redhat.com> - 2015-06-23 01:00 +0200
  [PATCH 0/3] percpu-rwsem: introduce percpu_rw_semaphore->recursive  mode Oleg Nesterov <oleg@redhat.com> - 2015-06-29 02:00 +0200
    [PATCH 2/3] percpu-rwsem: don't use percpu_rw_semaphore->rw_sem to  exclude writers Oleg Nesterov <oleg@redhat.com> - 2015-06-29 02:00 +0200
    [PATCH 3/3] percpu-rwsem: introduce percpu_rw_semaphore->recursive  mode Oleg Nesterov <oleg@redhat.com> - 2015-06-29 02:00 +0200
    [PATCH 1/3] rcusync: introduce rcu_sync_struct->exclusive mode Oleg Nesterov <oleg@redhat.com> - 2015-06-29 02:00 +0200

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